Utility meters, for example, electricity meters, often employ microprocessors to obtain comprehensive information regarding consumption of a monitored commodity by a facility or system. In the past, mechanical counter-type meters could only provide limited information such as the accumulated total quantity of electricity, gas, or water consumed. However, current processor-based meters have the capability of providing a variety of functions related to the monitored commodity. For example, processor controlled electricity meters are able to provide one or more of the following functions: voltmeter, watt meter, VA meter, distortion indicator, ammeter, VAR meter, phase angle meter, and phase rotation meter. Additionally, such meters are able to perform usage analysis such as load-profiling as it is known in the electricity metering industry, demand analysis to identify high demand periods during a day or a month, time of use metering to evaluate cost rates that vary according to the time of day, and diagnostics of both the meter and the system to which it is connected. In the case of electricity meters, such advanced capabilities still require fundamental metering measurements, such as voltage, current, energy and reactive energy. The processing device uses the fundamental measurement information (and a real-time clock if necessary) to perform any or all of the above advanced functions.
One problem facing the industry is that with so many functions available, there is a need to allow energy customers and/or utilities to define what functions they desire their meters to perform. Energy customers typically fall into one of three classes: high end users, commercial users, and residential users. High end users are typically energy producers who want to monitor energy parameters at distribution nodes and switching yards. Commercial users include manufacturing facilities as well as office and retail complexes that have a meter for each machine on a manufacturing line or a meter for each tenant, respectively. Residential users are single family dwellings with meters for measuring usage on a billing cycle basis. High end and commercial users are likely to want to have some control over the functionality implemented by a meter while a utility probably controls the type and number of functions performed by meters for its residential customers.
Until 1997, the data and functions used in meters and available from meters were typically proprietary concerns of the meter manufacturers. In 1997, ANSI promulgated its C12.19 standard to provide interoperability for programmable meters. These standards were developed to define a set of flexible data structures called tables for use in metering devices. The standard also formulated a protocol for identifying and describing these tables. Additionally, the standard included manufacturer-defined tables in an effort to support further flexibility. The data stored in these tables control how the meter processes data, what calculations it performs, and what outputs it produces. These functions include the time and date with support for daylight savings time, time of use rates, total usage monitoring, rate calculations, a list identifying the items to be displayed by the meter, and timing parameters for relay control. The table data organization is an improvement over the previous industry practice, which was to write custom software to perform all of these functions.
The tables defined by ANSI C12.19 are organized by decades. The Decade0 tables are configuration tables for a meter. Table00 in Decade00 is a general configuration table. Among the data included in this table are two data fields, one of which identifies the standard tables to which data may be written and the other of which identifies the manufacturer tables to which data may be written. The data placed in these fields is determined by the manufacturer of the meter. The Decade4 tables are security data tables for the meter. A list of passwords may be stored in Table42. Each password is for a group level. A default data field for each group level is maintained in Table43 that defines the tables in the meter that a user presenting the corresponding password may read/write or read only. Data that modifies the group access data stored in Table43 is stored in Table44. Thus, during a communication session, a meter may communicate with an external device to determine its group level and respond to its read and write requests in accordance with the data stored in Table43 and Table44.
While the data structures of the ANSI standard promote open platform access for metering devices, the structure suffers from some limitations. One limitation is the possibility that a meter manufacturer may limit a particular group's access to a data table to be read-only. Consequently, an external device at a manufacturer's facility or in the field communicating with a meter may be denied access to write data to one of the data tables within a meter. One example of a need to write data into an inaccessible table may occur when a field technician determines that a meter is out of calibration. As a result, the technician may need to write new calibration parameters into the meter's memory in order to bring it back into calibration. If the equipment used by the technician cannot supply a password to the Decade4 tables for a group that is authorized to write data into the appropriate table, the meter cannot be brought into calibration. Another limitation may occur when a factory or field technician needs to write a procedure or operational data into a data table to upgrade the meter's capability. Again, the Decade4 security tables may deny the equipment used by the technician to write data into the appropriate table. However, assigning a group level to the field service or factory device may grant the device access to data areas other than those required for effective servicing. Furthermore, setting group level access codes to values that accommodate occasional needs is overkill and may subject the meter to unauthorized tampering. Probably the most frequently occurring need arises when meter functions are modified or new meter functions are added at a factory or in the field. This task is also adversely impacted when the external devices used by the factory or field personnel are not authorized to modify particular tables within a meter.
What is needed is a way of occasionally bypassing the security provided by the Decade4 tables so that data may be written into ANSI C12.19 data tables.
What is needed is a way of screening access attempts to write data into ANSI C12.19 data tables that selectively enables data writes into data tables that are read only for a particular group level.